We examine how accretion on to T Tauri stars may be modulated by a time-dependent ‘magnetic gate’ where the inner edge of the accretion disc is disrupted by a varying stellar field. We show that magnetic field variations on time-scales ≪ 10 yr can modulate the accretion flow, thus providing a possible mechanism both for the marked photometric variability of T Tauri stars and for the possible co...

Algebraic multigrid (AMG) is an efficient multilevel method for solving large sparse linear systems obtained from the discretisation of scalar elliptic partial differential equations. AMG can be used to compute powerful preconditioners for use with Krylov subspace methods. We report on the design and development of an efficient, robust and portable implementation of AMG that is available as pac...

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a ‘‘classical’’ biological control program was initiated and...

Reconstructing a 3Dmodel of a human face fromamonocular video sequence is an important problem in computer vision, with applications to recognition, surveillance, multimedia, etc. However, the quality of 3D reconstructions using structure frommotion (SfM) algorithms is often not satisfactory. One of the reasons is the poor quality of the input video data. Hence, it is important that 3D face rec...

We present the results of an analysis of ultraviolet observations of T Tauri Stars (TTS). By analysing emission measures taken from the literature we derive rates of ionizing photons from the chromospheres of 5 classical TTS in the range ∼ 10 41 –10 44 photons s −1 , although these values are subject to large uncertainties. We propose that the He II/C IV line ratio can be used as a reddening-in...